Spinosaurus
Spinosaurus, meaning "spine lizard/reptile", is a very large theropod dinosaur from Africa. It lived through the Albian and Cemonian stages about 103–93 million years ago. According to modern size estimates, Spinosaurus was the longest known theropod dinosaur of all time, even longer than'' Mapusaurus, Tyrannosaurus, ''Giganotosaurus and Carcharodontosaurus. It was in fact related to neither, being a spinosauroid, the group that also contains Baryonyx and Irritator, but also dinosaurs such as Megalosaurus and Eustreptospondylus. Spinosaurus is a fairly well-known dinosaur in the public eyes, with its distinctive spinal extensions, elongated skull and large size. Sadly, the holotype fossil was destroyed in the second World War after the museum it was contained in was bombed by the allies, and for many years Spinosaurus was a forgotten dinosaur. Two species have been named, S. aegyptiacus and S. morrocanus, although the latter may simply be a synonym of the former. Description Modern maximum size estimates range from 12-16m long and 7-14 tonnes in weight making it the largest known theropod by some margin. Several recent estimates, notably those of Henderson (2007) and Dal Sasso have come up with higher weight esitmates (up to 20 tons). However, the lower lengths and high weight estimates have been criticised for issues including the skull reconstructions and methology of the study. Therrien & Henderson's estimate has been critisized because it based Spinosaurus's size on carnosaurs and tyrannosaurids, leading to excessive weight estimates but low size estimates. According to an estimate by Cau on his theropoda blog, Spinosaurus was up to 12.9t in weight, (estimated by scaling up the holotype from Baryonyx based on the 10th dorsal and then scaling up again to the size of MSNM V4074 via skull length) exceeding even the greatest weight estimates for other theropods. However, Andrea Cau recently stated he did not belive Spinosaurus exceeded 13m in length, which seems to go against all other studies on the length of Spinosaurus. Dal Sasso (2005) estimated Spinosaurus at up to 9 tonnes. However, Therrein and Henderson (2007) noted that if the square-cube law is taken into account, Spinosaurus could be anywhere from 11.7 to 16.7 tonnes. They then proceeded to estimate Spinosaurus at up to 20 tonnes via their equation. Its skull was very large, at 1.75m long it was the longest of any spinosaurid and one of the longest of any known theropod, perhaps being only shorter than the long skulled Giganotosaurus (although Scott Hartman's new estimate of 160 cm may change this).. It possesed a small flutted crest in the region in front of the eyes. This may have been brightly coloured and used for display. Sail On its back were tall neural spines with estimates for their max height ranging from 1.5-2m. It has been suggested that these spines held up a skin sail and used it for thermoregulation and display. However, the spines were not thin, but thick rods like seen in the fatty humps of modern day Bison. This has lead some to suggest that the spines held up a fatty hump. Regardless of their use, some sort of environmental pressure seemed to be forcing animals to grow some sort of sail. The un-related African iguanodont Ouranosaurus and its contempory theropod Suchomimus both possesed extended neural spines, While at the same time the north american carcharodontosaurid Acrocanthosaurus also had similar spines running down its back. Dimetrodon had thin spines that supported a skin sail]] Fossils Spinosaur fossils in general are very rare, and Spinosaurus is no exception. There are very few Spinosaurus remains that have been found, out of these the Holotype is the most complete. Specimens Six partial specimens of Spinosaurus have been described. The probable size of these individual spinosaurs can be estimated using comparison to known material from other spinosaurid dinosaurs. The estimates below are based on the Theropod Database and Dal Sasso et al., 2005. IPHG 1912 VIII 19, described by Stromer in 1915 from the Bahariya Formation, was the holotype. This specimen, from a subadult individual, was destroyed in World War II. However, detailed drawings and descriptions of the specimen remain. The individual is estimated to have been around 14 meters (46 ft) long and to have weighed about 6.7 tonnes (7.4 short tons). The material consisted of a maxilla (upper jaw) fragment, an incomplete dentary (lower jaw) measuring 75 centimetres (30 in) long, (the skull is estimated to have been 1.45 meters (5 ft) long with a mandible approximately 1.34 meters (4 ft) long), nineteen teeth, two incomplete cervical vertebrae, seven back vertebrae, dorsal ribs, gastralia, and eight caudal centra. The longest preserved vertebral spine was 1.69 metres (5.5 ft) long. ParisCMN 50791, described by Russell in 1996 from the Kem Kem Beds of Morocco, is the holotype of Spinosaurus marocannus. The material it is based on includes a mid-cervical vertebra which is 19.5 centimetres (7.7 in) long, an anterior dorsal neural arch, an anterior dentary, and a mid-dentary. MNHN SAM 124, described by Taquet and Russell in 1998 from Algeria, consists of partial premaxillae, partial maxillae, vomers, and a dentary fragment. They came from an individual estimated to have been about 14 meters (46 ft) long and to have weighed about 6.7 tonnes (7.4 short tons). The skull is estimated at approximately 1.42 meters (5 ft) long. Office National des Mines nBM231, described by Buffetaut and Ouaja in 2002, consists of an anterior dentary from the Chenini Formation of Tunisia which is very similar to existing material of S. aegyptiacus. Specimen MSNM V4047 of S. aegyptiacus, described by Cristiano Dal Sasso of the Civic Natural History Museum in Milan and his colleagues in 2005 from the Moroccan Kem Kem Beds, consists of premaxillae, partial maxillae, and partial nasals, which together measure 98.8 centimetres (38.9 in) long. The massive skull is estimated at 1.75 meters (6 ft) long, and the entire animal was estimated to have been around 16 to 18 metres (52 to 59 ft) in length and weighed around 7 to 9 tonnes (7.7 to 9.9 short tons), although it is probable the actual weight of the animal was higher. 'MSNM V4047 also possessed the impressions of a vertabrae embedded in its tooth row. Dal Sasso et al. tentatively identified it as belonging to Onchopristis, a large 8 meter long sawfish. UCPC-2, also described by Dal Sasso et al. in 2005, consists of a 'fluted crest' from the region in front of the eyes. Other known specimens consist mainly of very fragmentary remains and scattered teeth. For example, teeth from the Echkar Formation of Niger have been referred to S. aegyptiacus. Possible material belonging to Spinosaurus has also been reported from the Turkana Grits of Kenya and the Cabao Formation of Libya (which dates to the Hauterivian stage), though the assignment of the later to the genus Spinosaurus is tentative. Jack Horner in an interview about Jurassic Park 3 mentioned a huge 8ft (~2.5m) Spinosaurus''skull that he said would come from an animal 60ft long (or 18.3m). However, MSNM V4074 had a skull measuring only 1.75m long, yet it would not measure more than 16m long based on other spinosaurids. Indeed based upon other spinosaurids, a 2.5m skull would come from a Spinosaurus over 24m long and probally in exccess of 30t in weight. A specimen that is held in a private collection, nicknamed 'Tuscon Rock Show' is also rumoured to be a 2.5m long skull and may even be the specimen Horner was refering to. Until either of these specimens are published, however, it is unwise to consider these figures accurate. Lifestyle Diet and bite mechanics ''Spinosaurus and its relatvies have been a puzzle to scientists for quite some time. Their crocodilian-like skulls and conical teeth seem ill suited to hunting large prey. This has lead to the now common place suggestion that Spinosaurs in general were specialized fishers. However, some Spinosaurs (specifaically Irritator and Spinosaurus) have much more crocodile-like jaws. Also Spinosaurus ''itself was the second largest animal in its environment. This combined with a ''Baronyx being preserved with Iguanodont bones in its stomach, could mean at least Spinosaurus was a hunter. Some notable adaptations for withstanding forces in the skull include the cross section of its rostrum, the nasal crest as a point of discharge of the forces, and most particularly the presence of a strong secondary palate(crocodilians have this as well) which is an adaptation partly for resisting torsion that comes from biting into prey and the subsequent struggle that comes with it. Also the fact that its nostrils are placed so far back means before that point, the skull is entirely made of compact solid bone; this would be another adaptation for strength. It's teeth were deeply rooted within the skull allowing them to withstand high forces without breaking. Roughly 50% or more of each tooth was buried within the skull. Also the fourth tooth in the Maxilla was in line with the jaw muscle meaning more force was excerted by that tooth, which was also the largest tooth in the whole jaw at between 5 and 6 inches (between 12.7cm and 15.2cm) . The teeth had a D-shaped cross section, akin to Tyrannosaurus teeth. The rear portion of Spinosaurus' skull is typically renedered as very wide, around the magnitude seen in Tarbosaurus. From a birds eye view, it has a skull that resembles the prehistoric reptile Champsosaurus. Champsosaurus, despite having a very Gavial esc jaw, and its whole body length being a mere 5ft, had a bite force roughly equal to that of a large Grey wolf. So, although it is speculation, it is very reasonable to think that Spinosaurus had a very strong bite, stronger than the ill suited Carcharodontosaurids, but not as powerful as some tyrannosaurids. The potential prey of Spinosaurus could include many species of fish, crocodylomorphs and juveniles of the many sauropods alive at the time. Many animals in its environment were small compared to Spinosaurus. Infact, Spinosaurus was roughly 70% larger at least than all its contempories barring Paralititan, a rare case for a carnivorous animal. Habitat At the time of Spinosaurus ''living in Africa, Africa was a desert with scattered poccets of marshy terrain which were home to Spinosaurus. ''Spinosaurus's massive size has in the past lead some to suggest Spinosaurs in general may have been semi-aquatic. It has recently been confirmed that Spinosaurus was a semi-aquatic Theropod.http://geology.gsapubs.org/content/38/2/139 Whether Spinosaurus had a lifestyle like a modern day Crocodile or Gavial is unknown. However, Spinosaurus was found to be the least semi-aquatic out of the spinosaurids tested but still more aquatic than its surrounding contemporary dinosaurs. In The Media Spinosaurus was a forgotten Dinosaur until it featured in Jurassic Park 3 in 2001. It was shown to be larger and more powerful than Tyrannosaurus (though both of these large theropods were rather small in comparison to life size). the two engaged in battle resulting in a Spinosaurus victory. After Jurassic park 3, it featured in related merchandise, including Jurassic park Operation genesis for PS2, Xbox and PC. It was again shown being able to duel with Tyrannosaurus, though the outcome can go either way this time. It was also featured in the 2009 documentary titled Monsters Resurected, in which it was shown as the apex predator of its time. It did though have many innacuracies. Including pronated hands, Spinosaurus having a wider and more flat skull than in reality and Rugops being severely undersized. In life it was 9m long, however Spinosaurus was able to fit one in its jaws in Mosnters Ressurected (though this may have been a juvenile). Spinosaurus also took out Sarcosuchus (which it probally never encountered) and Carcharodontosaurus, it took out the latter with one swipe of the arm to the head. References Category:Spinosaurids Category:Middle Cretaceous dinosaurs Category:Dinosaurs of Africa Category:Theropods Category:Spinosaurines